As a system for protecting an occupant in the event of a car crash, Japanese Unexamined Patent Application Publication No. 10-217818 describes an occupant protection system in which the front of a seat cushion is increased in height or hardened during the car crash to prevent a so-called submarine phenomenon such that the occupant passes under a lap belt during a front crash even with a seat belt.
The occupant protection system disclosed in the patent has a recess in the front of a seat pan, in which an airbag is arranged.
A cylindrical inflator is disposed in the airbag, from which a stud bolt projects downward. The bolt passes through the airbag and a seat pan and projects downward therefrom. A nut is tightened to the bolt, so that the inflator is drawn to the seat pan and fixed thereto and the bottom of the airbag is clamped between the inflator and the seat pan; the airbag is thus joined to the seat pan.
With the occupant protection system described in the Japanese Unexamined Patent Application Publication No. 10-217818, the stud bolt of the inflator is passed through the hole of the airbag and further passed through the hole of the seat pan. The bolt, however, comes off easily from the hole of the airbag before the bolt is passed through the hole of the seat pan, having the problem of burdensome assembly work.